This invention relates to a trephine device for removing anterior epithelial cells from corneal surfaces. More particularly, this invention relates to a trephine device for removing anterior epithelial cells from corneal surfaces using removal means operated by the surgeon without affecting the underlying corneal tissue, typically prior to the use of an excimer laser to reshape the anterior surface of the cornea.
The use of an excimer laser to reshape the anterior surface of the cornea of the eye to correct refractive defects and other problems is well known to those skilled in the art. It is also well known to those skilled in the art that each pulse of the excimer laser ablates a fixed depth of corneal tissue, with the depth depending on the homogeneity of the tissue and the power output of the laser. For this reason, the superficial layer of epithelial cells or epithelium on the surface of the corneal area to be reshaped must first be uniformly removed since the nucleus and surrounding cortex of the epithelial cells will cause the excimer laser to ablate at a different rate, thereby causing a roughening of the surface of the underlying corneal tissue (i.e. "Bowman's membrane" and corneal stroma) after the epithelium has been ablated. At the present time, the epithelial cells are removed manually by the surgeon using a scraping procedure prior to excimer laser corneal reshaping. However, it is apparent that this procedure requires considerable skill and, if it is not performed perfectly, or nearly perfectly, will result in the uneven removal of the epithelium which will lead to the concomitant uneven ablation of the corneal tissue which is subjected to the excimer laser energy pulse and even the possibility of further detrimental effects to the patient such as corneal scarring and the like. In view of the foregoing, it would clearly be advantageous to employ a device which safely and effectively removes the entire epithelium from the area of the cornea to be reshaped without affecting the underlying corneal tissue prior to excimer laser reshaping of the cornea.
The use of trephine devices for cutting a groove or slit in the cornea or for surgical removal of the cornea is well known to those skilled in the art. For example, U.S. Pat. Nos. 4,763,651 (Kaufman et al.) and 4,750,491 (Kaufman et al.) disclosed a trephine device for cutting a groove in the cornea so that replacement corneal tissue may be tucked into the groove and sewed into place. U.S. Pat. No. 4,336,805 (Smirmaul) discloses a trephine device to remove corneal "buttons" in cornea replacement surgery, as does U.S. Pat. No. 4,190,050 (Bailey). However, a trephine device useful in removing the corneal anterior epithelial cell layer prior to excimer laser reshaping of the cornea, without affecting the underlying corneal tissue, has not previously been disclosed.
It is the object to this invention to provide a trephine device for removing anterior epithelial cells from a corneal surface, without affecting the underlying corneal tissue. It is one feature of this invention that the trephine device employs removal means integral to the housing which may be at least one rotating cutting blade or at least one oscillating cutting blade adapted to conform substantially to the shape of the cornea, or other removal means such as ultrasound activation, to achieve removal of the anterior epithelial cells without affecting the underlying tissue. Since the epithelial cells are relatively gelatinous, it is another feature of this invention that the epithelial cells excised from the area of the cornea to be reshaped by the excimer laser may be transported away from the corneal surface by means such as suction, or in another embodiment, are projected or impelled by the cutting blade or blades through at least one aperture located in the side walls of the trephine device, thereby allowing the epithelial cells to be deposited on the peripheral surface of the cornea where they may thereafter be removed by swabbing or suction techniques.
The present invention is advantageous in that it allows the surgeon uniformly to remove the anterior epithelial cells from the corneal surface without damaging the corneal tissue, e.g. Bowman's layer. By providing a uniform corneal surface to be reshaped by the excimer laser, roughening the underlying corneal tissue due to an uneven ablation of the epithelium is substantially eliminated.